shades of doubt
by bravevulnerability
Summary: 'He may not be thrilled to see her, he may have given up on her six months ago, but her heart still fluttered at the sight of him.' An AU take on 5x05, Probable Cause.


**A 'what if' scenario of sorts. Castle ended his partnership with Beckett and the Twelfth after 4x22 (Undead Again). **

* * *

Kate scrawled her signature across the bottom of the page and rose from her seat, headed to the break room for her fourth cup of coffee that day. She didn't drink from the espresso machine anymore, found it too complicated, too painful, to attempt garnering a cup of caffeine from the contraption that never worked for her anyway. Castle had never taught her how to operate it properly; she had never tried to learn. She had always thought he would be around to make her coffee for her.

She sighed, preparing her taste buds for another cup of flavorless, black sludge from the ancient coffeemaker shoved in the corner of the room. But the sound of a commotion coming from the elevator had her curiously poking her head around the door of the break room.

Her jaw dropped at the sight of Castle being led through the homicide floor with his hands behind his back. He caught sight of her as he struggled against the officer guiding him towards one of the open interrogation rooms.

"Kate!" he called out and for a moment, she was frozen, unsure if her imagination had drawn up a hallucination after so many restless nights of little sleep, but then he shouted her name again, had the entire floor's attention swinging to her, and she hastily strode across the bullpen, moving to stand in front of him, attempting to protect him from her own people.

"What the hell is going on here?" she demanded, her voice not quite as strong as she would have liked.

"He's our number one suspect for murder, Detective Beckett," LT explained and her eyes flickered to Castle's in question, but he was already vigorously shaking his head.

"You know I would never do this, you know me. _Kate-_"

"Can I have a moment with him?"

"Once we get him into interrogation," LT answered quietly, giving her a sort of sympathetic look that she hated.

Beckett nodded and took a step back.

"Don't say anything," she told Castle for good measure and although his eyes were dark and panicked, not looking at all happy to see her, he did look grateful as he nodded back.

He may not be thrilled to see her, he may have given up on her six months ago, but her heart still fluttered at the sight of him.

* * *

She impatiently waited in the observation room for officers to escort Castle inside interrogation two. She had read over the case file of Tessa Horton while she waited, cringed at the crime scene photos. Whoever had killed this woman had done it in a truly sadistic way.

Nothing could convince her that Richard Castle was capable of such a gruesome act, of carving a strange symbol into the skin of the victim's forehead and hanging her from a ceiling with barbed wire. He was capable of writing such things, she could buy into that much, but she knew him - well, she _had _known him - and he would never be able to stand committing such a grisly murder.

As soon as they gave her the all clear, Kate closed the file and slipped inside the interrogation room, sat down across from him. Under the harsh lighting, she could see how ragged he looked and not just from the troubles this evening in particular had brought him. He'd lost a lot of weight, his cheeks visibly hollowed, his dress shirt a little too loose, and exhaustion had settled in permanent lines along every crevice of his face.

He appeared almost as miserable as she had felt over the last few months.

"Are you working my case?" he asked, a hint of hopefulness to his voice, but she shook her head.

"I'll try to be a part of it as much as I can, but unless Gates grants permission, there isn't much I can do yet."

"They're trying to accuse me of murder, Beckett," he told her incredulously, combing his fingers through his hair for what must be the hundredth time in the last hour. "I would never-"

"I know you wouldn't," she affirmed, impulsively reaching across the table to touch his hand, but he jerked it back from her and it _hurt_, but she withdrew her fingers, clasped her hands in her lap. "I don't know what's going on, but I will get to the bottom of this."

"Yeah," he murmured, keeping his eyes downcast. "I hope so."

* * *

She found him hunched over in his cell a couple of hours later, head in his hands, elbows piercing into his thighs, but he startled at the sound of her standing at the front of his cell.

"Beckett," he sighed, scraping his hands through his hair. "What do you want?"

"To check on you," she offered quietly, uncertainly. She had hoped he would want company. Maybe he did, just not hers. "How did the visit with Alexis and your mom go?"

"Horrible," he snapped. "Satisfied?"

She ignored the harshness of his tone, swallowed hard before curling her fingers around the steel bars of his cell.

"I'm going to figure this out," she swore to him, intent on ensuring him until he believed her. "Whoever is behind this, whatever is going on, I will figure this out and then I will get you out of here, Rick. I promise."

Castle glanced up to see her, his eyes lifeless and his face slackened with fatigue.

"Your tenacity is inspiring, Beckett. Always has been. But it isn't enough," he answered. It wasn't meant to hurt her; it was spoken as a fact, not an insult, but it still felt like one.

"Well, it's going to have to be."

"Listen, I understand you're trying to do me a favor, make it like it was before, but it's just never going to happen, okay?"

Her breath caught in her throat and she feared she was going to start coughing when she couldn't quite remember how to make it come back up.

"Castle-"

"Will you just go?" he grumbled, rubbing at his eyes.

"I love you," she blurted, gracelessly, stupidly, and his head snapped up and _oh god_, what had she just done?

The panic flushed through her bloodstream like ice water, made her mouth go dry, because she had never said the words aloud, not once outside the safety of her head, but here she had just admitted them to him like a desperate idiot. He looked just as shocked as she felt and his lips parted as if to speak, but she went on before he could say anything. Might as well. "I know you left and you said we were done, but I loved you, Castle. And it - that never changed. You may not feel the same, but that doesn't mean I want you to rot in a cell, especially for something you didn't do."

His eyes widened, the dark blue flashing with anger like lightening in a storm.

"_I_ didn't feel the same? I was the one who was able to say the words, _you_ were the one who hid from them, pretended they never happened," he growled, standing up only to pace away from her.

"I was afraid," she defended, knuckles whitening against the cage of the cell. "I needed time and I was so close. But then you decided you were done waiting."

She was suddenly glad the cell wall was between them; he looked like he wanted to throttle her.

"No, what I did was give up on a lost cause. I heard you in that interrogation room, after the bombing case. You remembered the whole time and you _lied_ about it. You loved me back, Kate? You sure didn't show it," he muttered and she blinked rapidly against the tears. Now was not the time to cry. She had cried enough and she would not cry in front of him. But the tears kept welling up and leaking out and she lowered her head, tried to hide them.

"I wanted to be more," she whispered to the floor. "I was in therapy, trying to be better, to be - I wanted to be more for you."

He was silent and she was too scared to lift her head, to see the disgust lining his face. He didn't want her, she'd missed her chance, and now it was time to go, free him of this false accusation and let him walk out of her life for the last time.

She was just about to drop her hands when his fingers slipped over hers through the square holes of the cell, his index and middle finger covering hers, and she glanced up in bewilderment.

"I didn't need more. I just needed you," he sighed, brushing his thumb over hers in a gentle caress. The anger hadn't gone from his face, there were still traces lingering and he still looked exhausted, but above it all, she could see he appeared lighter, more hopeful, even slightly apologetic, and she curled her other hand around the lock, deftly inserted the key she had impulsively snagged from the front desk.

"Kate," he warned when he realized what she was doing, but she ignored him, slipping inside his holding cell and soundlessly closing the door behind her.

"I'm so sorry, Castle," she breathed, cradling his face in her palms, delicately tracing her thumbs over the darkening smudges of purple beneath his eyes. "I should have just - I'm sorry."

He placed tentative hands on her waist and she rose up on her toes, brushed her lips over his once, twice, before giving in to the soft flesh of his mouth.

The fingers curled around her hips tightened as his lips remained unmoving against hers, but slowly, he drew her closer, circled his arms around her, hauling her body against his and not loosening his grip once she was sealed to him. Kate reveled in the crush of her ribcage, the burn in her lungs as he kissed her, desperate and hot and just like she remembered. She gasped when his tongue slipped past her lips, but she only canted her forward, did her best to hold on through the delicious assault.

But all too soon his lips were jerking away from hers and he was stumbling backwards with her still in his arms.

"We can't do this."

"No, Castle, please," she moaned. He couldn't give up on her, not after he had kissed her like that. "I can be-"

"No, I meant here, Kate," he breathed, lifting his hand to rest at her jaw, brushing his thumb over her swelling bottom lip. "We shouldn't be making out in a holding cell."

The tight tension in her shoulders loosened and she relaxed against him.

"Probably not," she sighed.

"After this, we're going to talk long and hard about what we are, what we both want," he instructed and she nodded earnestly, clutched at his lapels for emphasis.

"All I want is you," she whispered, staring up at him, a hint of pleading in her eyes, needing him to believe every word because she could not lose him again. Never again. "I just want you, Castle."

The last of the indecision is his eyes ebbed away, the hard blue crystal softening, and he tilted his forehead to hers, stroked a hand through her hair.

"Worst timing," he huffed with a flicker of a smile and she choked on a laugh.

"Always the worst," she conceded, but nudged her nose forward, into his cheek until he kissed her again.

"I missed you so much," he admitted between gentle kisses that he struggled to keep chaste.

She locked her arms around his neck, grazed her fingers through the disheveled field of his hair, smoothing the soft locks and cradling the back of his skull in her hands.

"Me too," she whispered. "So much, Castle. I should have tried to explain. I shouldn't have let you leave. I couldn't even - I've hated it without you."

"Me too," he echoed, folding her into his long arms and holding her close.

She pressed her nose to the side of his throat, inhaled the heady scent of him she had been so long without and trailed her nails up and down his back to soothe.

"Well, isn't this sweet."

Castle froze, but then he was immediately using the arm around her waist to push her behind him before she could even recognize the voice on the wrong side of the bars.

"You two should be grateful I turned the security cameras off. Wouldn't want such unprofessionalism captured on film, would we, Detective Beckett?"

Kate's eyes instantly flew to the camera, but the red light signifying the camera was currently not filming flashed back at her mockingly.

"Tyson." Castle muttered the name, his hand flexing over the bone of her hip, but Kate stole the hand away, moved to stand beside him rather than behind.

She subtly attempted to draw her gun, but Tyson lifted his, Ryan's service piece, and aimed for her.

"Tell her to put it down or I shoot out her kneecaps," he said to Rick and Castle turned his eyes to her.

"Kate," he pleaded, only loud enough for her to hear, and she reluctantly lowered her weapon but refused to holster the piece, glaring at Tyson even though his attention was solely on Castle now.

"You're behind this," Kate growled. "You killed Tessa."

"Oh, no. She's not my type. I prefer blondes, remember?" He grinned between the two of them. "Here's a much more believable story - writer boy here killed Tessa. It practically writes itself, right? After all, he commits murder every day in his mind for his books. It's not hard to imagine that he'd eventually... cross the line."

"Why are you doing this, Tyson?" Castle demanded, squeezing her hand, crushing the small bones together, but she hardly noticed.

"Four years, Castle. I gave up four years of my life planning the perfect vanishing act so that the cops would stop looking for me, so that I could begin again, could begin killing again, so that I could taste that fear again. Four years. You ruined it."

Kate had never witnessed Tyson truly angry, had never known the signs or his tells, but as she watched him stare Castle down with a quiet rage in his black eyes, she knew this was what his anger looked like.

"Well, if it's revenge you wanted, why not just kill me?" Castle questioned, his voice cool and calm, but Beckett felt her hand go clammy in his.

"Where's the fun in that? Oh, no, no, it's more fun to destroy you. Why do you think I let you live that night in the motel?" he asked. "People think it's killing that I like, but murder's just an act. It's all about the anticipation, the planning. Watching you and your daughter taking a walk…"

Castle stiffened beside her, the tension diving down his spine.

"It's hearing you get yourself off with her name in your mouth almost every night," he added with a sick smile, tilting his head towards Kate in indication and she felt her stomach twist. "Standing in your living room, being inside your life knowing that I'm going to take it all away from you. That's what I like."

"You won't get away with this," Kate snarled.

"Oh please, what are you going to do? You going to tell them that I came here? You think they're going to believe the lies of a desperate man and his loyal detective girlfriend?" He huffed a hollow laugh and cut his eyes back to Castle. "She can't save you. There's no time. When the D.A. files charges tomorrow, they're going to send you to central booking – the tombs. I have people waiting for you. You won't last the night. And that'll be her punishment." He looked to Kate again, a wicked lift of his lips forming. "Believing that you were innocent and not being able to stop it. It'll haunt her for the rest of her life, won't it, Kate?"

Castle jerked forward, but she gripped his arm, dug her fingers into his bicep.

"It's a shame really, that this reunion happened just a little too late. Or perhaps too early. That's going to leave even more regrets for Detective Beckett," he sighed, shooting her a pitying glance. "Lucky for you, Castle, you'll be dead."

Tyson kept his eyes on Rick, watching him until he disappeared into the shadows, and Beckett swiftly reached for the unlocked cell door, shoved it open and raised her weapon.

She followed Tyson's footsteps, swept the entirety of lockup, but couldn't locate where he had disappeared to or how.

"Fuck," she growled, fishing her phone from her back pocket and texting Esposito, filling him in with as little detail as possible and telling him to get an APB out on 3XK.

"Kate." She spun at the sound of Rick's voice.

"We'll find him," she insisted. "We know his face, we know-"

"We know how good he is at disappearing," Castle grumbled, defeat in his eyes but she shook her head against it.

"He's still human, he'll make a mistake. He may be smart, but he can't hide forever. C'mon, we-"

"I can't leave," he sighed when she snagged his hand, attempted to pull him towards the exit. "Suspect in custody, remember?"

"I'm not leaving you here, it isn't safe," she protested, curling her hands around his forearms.

"He won't try anything. He told us his plan knowing no one will believe us. He knows nothing will interfere with it. I'll be safe for the night," he assured her and shit, she wanted to cry again, for him, for them, for this entire fucked up situation. "Do what you can while we have the time."

She bit her lip, still hating everything about this, but nodded, every part of her screaming against the idea of leaving him alone and unguarded from the evil lurking in the darkness.

"If not, if we can't... I'm getting you out," she whispered, just in case. "We'll go."

His brow furrowed before his eyes widened in understanding.

"Beckett-"

She silenced him with a kiss, meeting his mouth with a bruising intensity, silently promising him it would be okay no matter what.

"For tonight, just be safe," she murmured against his lips and he hesitated, but nodded before breaking away from her and going back into his cell, sliding the door closed so that the steel bars separated them once again.

* * *

Kate came for him the next morning, handcuffs out and ready.

"This was not how I imagined our next encounter with your cuffs would go," he chuckled and she tried to smile for him, but it fell flat, just like the light in his eyes.

"Do you remember the first time you handcuffed me?" he murmured, throwing in a mention of the New York public library and how angry she had been with him, reminiscing about memories like they wouldn't get the chance to ever speak about them again. "What I wouldn't give to be there now."

She curled her fingers around his wrists, stroked her thumbs over the throb of his pulse, willing her own frantic heartbeat to calm.

"This isn't over," she whispered, wary of the officers listening in. "I promise you, I will get you out."

Castle stepped closer, holding her eyes with a sad smile as he maneuvered his hands to twine with hers. "It's okay."

"Rick-"

"Whatever happens," he insisted, his hands squeezing, his eyes narrowing, as if he was trying to tell her something, but she couldn't comprehend what. "It's okay."

Kate nodded, but was unable to believe him. She wouldn't give up though, not now that she finally had him back. She wasn't sure how, but she would find a way to change the fate Jerry Tyson had laid out for them. And then she would put the son of a bitch in the ground.

* * *

They stood at the edge of the bridge, staring down at the river where Tyson had fallen to his supposed death, but she knew Castle didn't believe for a second the man was truly gone. The divers hadn't found a body.

"Rick," she murmured, stepping into his side, curling her fingers into the crook of his elbow.

He glanced to her curiously, the little touches between them still so new and foreign, but so good.

"I have some vacation days saved up," she told him, a little timid, momentarily diverting her eyes to the ground before forcing them back up to meet his. "Did you maybe want to get out of town for a while?"

"With - with you?" he asked a bit too incredulous, and yeah, okay, bad idea. She made to move away, but he caught her retreating figure by the waist, laid a gentle palm over the sharp jut of her hipbone. "That sounds amazing. I have Mother in the Four Seasons, Alexis is living at her dorm in Columbia, and I don't want to go back to the loft. Not until it's thoroughly debugged."

She nodded, lowering her eyes once more, shyly, because she had basically just asked him to go away with her and she wasn't even sure where to go.

"My house in the Hamptons would be a nice retreat for us," he threw out, as if reading her worries. "It's secluded, safe, and it'll give us the privacy to talk."

She could practically feel his eyes resting on her, waiting to see if what she had said and done in lockup the other night still held true.

"It sounds perfect," she replied, lifting her gaze and smiling up at him. "I'll talk to Gates, pack a bag. We can leave tonight."

A flicker of excitement rippled across his features. "The sooner the better."


End file.
